Simplified collapsible container

ABSTRACT

A simplified container construction including a bottom framefixed pallet portion and a container portion mounted thereon, wherein wall boards for the side and end walls of the container are demountably erected in edge to edge relation within the bottom frame along the inside thereof in such a manner as to hold them together in position by use of an easily releasable holding means and a bottom board for the bottom of the container is demountably placed on the bottom frame-fixed pallet and within the erected wall boards, whereby the container can easily be assembled for shipping goods and disassembled as a compact size bundle of the component members thereof for being returned to the user for repeated use.

United States Patent 1191 Suzuki Mar. 12, 1974 SIMPLIFIED COLLAPSIBLE CONTAINER Primary Examiner-Donald F. Norton [751 v Inventor: Hiromasa Suzuki, Kudamatsu, Attorney Agent Flrm Frank Jordan Japan 57 ABSTRACT [73] ASsgnee: Nippon Zeon Ltd"Tokyo'-lapan A simplified container construction including a bot- [22] Filed; July 10 1972 tom frame-fixed pallet portion and a container portion mounted thereon, wherein wall boards for the side and [21] App]. No.: 270,201 end walls of the container are demountably erected in edge to edge relation within the bottom frame along [52} us. (:1. 217/13, 217/43 A the inside thereof in Such e manner as to hold them 51 1m. 01 B64d 19/16 together in Position by use of an easily releasable {58] Field f Search 217/13, 43 A, 45; 220 4 p holding means and a bottom board for the bottom of the container is demountably placed on the bottom 5 References Cited frame-fixed pallet and within the erected wall boards, UNITED STATES PATENTS whereby the container can easily be assembled for shipping goods and disassembled as a compact size 2 bundle of the component members thereof for being 3:451:572; 6/1969 Edmundson jfi...........:::::: 217/43 A returned to the for repeated 12 Claims, 17 Drawing Figures PATENIED AR 2 L974 sazznnr PATENTEDIAR 12 I974 SHEET 2 UP 3 FIG.I2

FIG.|3A FIG.|3B FIG-J4 SIMPLIFIED COLLAPSIBLE CONTAINER This invention relates to a construction for a simplified container and more particularly to a construction for a simplified container which is capable of easy and quick assembly and disassembly and is adapted as a general-purpose container and especially for storing and shipping elastomeric goods, such as synthetic rubbers, tending to be spontaneously defonned due to their inherent cold flow.

As containers for storing and shipping elastomeric materials such as synthetic rubbers, kraft paper bags, carton boxes and the like have hitherto been generally used. Such bags and boxes, however, are disadvantageous in that they after loaded with a synthetic rubber will soon tend to be deformed in conformity to the deformation of the synthetic rubber caused by its cold flow and to be often broken especially when stored in stacked relation.

The containers according to this invention eliminate such drawbacks as the conventional ones have had. It is to be noted that, as described later, a container in accordance with this invention comprises as one of the integral parts thereof a frame-fixed pallet portion on which a container portion is mounted.

The primary object of this invention is to provide a simplified container which can be easily set up for shipping goods and also easily knocked down so as to be sent back to the user as a compact size bundle of the component member thereof for repeated use as a container.

Another object of this invention is to provide a container adapted for shipping elastomeric goods which comprises a pallet on which a bottom frame is fixed, loose wall boards erected on the bottom frame-fixed pallet for constituting the side and end walls, separate upper wall edge frames or a unitary upper edge frame covering the upper edges of the erected wall boards for protecting these edges and, if these edge frames are separate ones, a means for holding the loose wall boards together in position.

Still another object of this invention is to provide a container which further comprises vertical wall edge frames in addition to the same component members as mentioned above, the frames covering the vertical edges of the wall boards held together in position.

A further object of this invention is to provide a frame-fixed pallet for mounting the container portion thereon.

In one aspect of this invention, the vertical wall edge frames may be used for reinforcing the vertical edges of the adjacent, side and end walls.

In another aspect of this invention, the separate upper wall edge frames may be used together with the vertical wall edge frames to securely hold the loose wall boards together in position with aid of an easily releasable holding means such as pack tapes wound around the wall boards.

In still another aspect of this invention, the unitary upper wall edge frame may be used in combination with vertical wall edge frames thereby serving as a means to securely hold the loose wall boards together in position and eliminating the use of a holding means such as pack tapes wound around the wall boards.

In a further aspect of this invention, the combined use of the unitary upper wall edge frame and vertical wall edge frames may be replaced by the combined use of the separate upper wall edge frames having a hinged metallic bar at one end of the outer side and the vertical wall edge frames having a hanger at the upper end of the outer side, the metallic bar being capable of being engaged with the hanger, to securely hold the loose or separate wall boards together in position without use of such a holding means as pack tapes wound around the wall boards.

In a still further aspect of this invention, the combined use of the unitary upper wall edge frame and vertical edge frames may also be replaced by the combined use of the separate upper wall edge frames having hangers at the ends of the outer side and the vertical edge frames, these upper and vertical edge frames being capable of being locked with each other by inserting a rectangularly bent metallic bar in the hangers of the adjacent upper edge frames, to securely hold the loose wall boards together in position without use of holding means such as pack tapes wound around the wall boards.

Reference is now made to the accompanying drawings: in which:

FIG. 1 is a perspective view of a pallet according to this invention;

FIG. 2 is a perspective view of a bottom frame to be fixed on the pallet of FIG. 1;

FIG. 3 is a perspective view showing an alternate form of bottom frame construction;

FIG. 4 is a perspective view of a bottom frame-fixed pallet prepared by fixing the frame of FIG. 2 on the pallet of FIG. 1;

FIG. 5 is a perspective view showing an embodiment of a container and illustrating the use of pack tapes and a lid which is optional in the constitution of this invention;

FIG. 6 is a view in vertical section illustrating how a container according to this invention is loaded with articles such as rubber bales by the use of a plunger;

FIG. 7 is a perspective view of an upper wall edge frame;

FIG. 8 is a perspectiveview of a modification of the upper wall edge frame of FIG. 7;

FIG. 9 is a perspective view of a vertical wall edge frame;

FIG. 10 is a perspective view of a modification of the vertical wall edge frame of FIG. 9;

FIG. 1 1 is a perspective view showing in detail the engagement of the vertical wall edge frames of FIG. 10 with the bottom frame of FIG. 3 and upper wall edge frame of FIG. 8;

FIG. 12 is a perspective view showing the engagement of a unitary upper wall edge frame with the vertical wall edge frames of FIG. 9 or 10;

FIG. 13A is a perspective view of a variation of the engagement of FIG. 11, and FIG. 13B is a side elevation showing the working of the engagement mechanism of FIG. 13A;

FIG. 14 is a perspective view of another variation of the engagement of FIG. 11;

FIG. 15 is a plan view partly broken away showing the upper wall edge frames covering the wall boards erected in position;

FIG. 16 is a perspective view showing another embodiment of a container; and

FIG. 17 is a perspective view showing still another embodiment of a container.

Referring now to the drawings and with particular reference to FIGS. 1-6, an embodiment of this invention comprises a pallet 1 on which a bottom frame 6a or 6b is fixed, side walls 7 and end walls 7a, a bottom board 9, upper wall edge frames 8a, a lid 10 made of longitudinal and transverse slats 11, 12 and pack tapes 15, 16 and 17. The pallet 1 comprises spaced parallel base boards 2, spaced parallel runners 3 preferably having sloped ends 3, spaced parallel longitudinal boards 4 and spaced parallel transverse boards 5. The runners 3 are fixed on the base boards 2 transversely thereof, the longitudinal boards 4 on the runners longitudinally thereof, and the transverse boards on the longitudinal boards 4 transversely thereof. It is essential that, in the pallet 1, these component members thereof should be generally arranged so that the pallet 1 has therein vertically free spaces 18 through which the tines 19 of a plunger 19 may be put into, or out of, the inside of a container construction to be fabricated. The component members of the pallet H are made preferably of wood and may be made of other material such as steel or plastics, for example, polyethylene, polypropylene, foamed polystyrene, polyvinyl chloride and fiber reinforced plastics. The fixing of one of the component members on another may be affected by means of nails 14, bolts, a synthetic resin adhesive or the like. The pallet 1 is provided thereon with the bottom frame 6a or 6b to form a bottom frame-fixed pallet Ha by fixing the frame on the pallet by means of nails 14', bolts or the like driven through holes 14 in the bottom frame or by means of a suitable synthetic resin adhesive, welding or molding when the pallet and bottom frame are made of plastics. The bottom frame 6a or 6b is generally rectangular in plan view and is composed of bars having a L-shaped cross section, such as angle steel bars, welded at the ends with each other so that they together form a rectangular shape. The frame 6/) is provided in the vertical side with projections which will be inserted in the lower holes provided in a vertical wall edge frame to be described later. The frames 6a and 6b are made preferably of steel and may be made of aluminum, wood or plastics. In the bottom frame-fixed pallet la, it is preferable that the runners 3 have the sloped ends 3', thus forming a wedge-shaped recess between the inclined end 3 and the portion of the longitudinal board 4 extending beyond the upper shorter edge of the end 3' as illustrated most clearly in FIGS. 1 and 5.. The thus-formed recesses of the frame-fixed pallet la allow the passage of rope therethrough to lift up and lower down the containers according to this invention for loading or unloading, thereby assuring easy and secure loading and unloading of the containers, whereas the passage of ropes through under the bottom of a conventional pallet has hitherto been the customary practice to lift up or lower down a conventional container mounted on the pallet especially in harbor loading or unloading operations. The pallet construction according to this invention further makes it possible to stack several of the containers one upon another for storage.

Referring particularly to FIGS. 5 and 6, square or rectangular side and end wall boards 7, 7a which are sized so that their lower portions are snugly received in the bottom frame 6a, are erected in edge to edge relation with their lower edges being positioned on the horizontal side of the bottom frame 6a snugly along the vertical side thereof to form the walls of the container and with their upper edge being covered by upper wall edge frames 8a having a channel-shaped cross section To protect the vertical edges of the erected wall boards, they may be covered with channel-shaped vertical wall edge frames in such a manner that the former are inserted in the recess of the latter. It is to be noted that these wall boards so erected in position are still loose or separate. The bottom board 9 is demountably placed on the frame-fixed pallet la within the erected wall boards 7, 7a. The loose wall boards 7, 7a so erected are kept in position without falling outward by binding the outside of the wall boards with the pack tapes 15. The bottom board 9 may be dispensed with in cases where the surface of the bottom frame-fixed pallet la is usable as the bottom for holding certain goods thereon. The container as shown in FIG. 5 may be further provided with vertical wall edge frames 13a or 13b shown in FIG. 9 or 10. Goods such as synthetic rubber bales, are charged into the thus-formed opentop container conveniently in the following manner.

With particular reference to FIG. 6, a cargo-handling plunger 19, for example, a three-forked plunger is inserted from under the pallet through the spaces defined by the longitudinal and transverse boards 4 and 5 into the inside of the open-top container to the point that the demountable bottom board 9 is raised by the tines 19 of the plunger 19 nearly to the top opening of the container, after 'which synthetic rubber bales 20 in this case are loaded on the raised bottom board 9 and then the board 9 is lowered through approximately the same height of the bales 20 for further loading other bales 20 in a desired packing arrangement on the previously loaded bales 20, and such loading procedure is repeated until the container is filled up with bales 20, thus making possible the use of an autopalletizer which has been believed difficult to use for loading goods in a box-type deep container of the type described. Cushions asindicated at 25 may be dispensed with.

The open-top container so loaded may be covered with the lid M] which comprises an optional feature of this invention and, if desired, the lid 10 consisting of crossed slats ll, 12 may be secured to the container body by using the pack tapes 16 and 17.

The wall boards 7, 7a are made preferably of wood or hardboard and may be made of plastics and, in some cases, steel. The bottom board 9 and the lid 10 are made of wood or hardboard and, in some cases, plastics. The upper wall edge frames 8a-8e are made of a metal such as steel or aluminum and, in some cases, of plastics. The pack tapes or bands may be made of a metal, preferably, steel.

In FIG. 5, the container construction comprises the bottom frame fixed pallet la, the side and end wall boards 7, 7a demountably positioned erect along the inside of the bottom frame 6a of the frame-fixed pallet 1a, the channel-shaped upper wall edge frames 8a, the lid 10 and the pack tapes 15-17 used to securely hold the various component members together. Thus, the container loaded is easily unpacked only by cutting the pack tapes 15-17 to allow the wall boards 7, 7a to falloutward, with the result that the load is easily and immediately taken out of the container. With the tapes cut and the load removed, the container construction may be dealt with as a compact side bundle of the component'members for being sent back to the user for repeated use as a container. This is achieved by, after disassembly of the container construction, placing on the bottom frame-fixed pallet 1a the bottom board 9, four loose wall boards 7, 7a, the upper wall edge frames 8a and the lid 10 and packing these members into a bundle thereof of compact size.

With particular reference to FIG. 16, another embodiment of this invention comprises the same essential component members as the container construction shown in FIG. 5 except that the bottom frame 6a and upper wall edge frames 8a are respectively substituted by the bottom frame 6b and upper wall edge frames 8b and that vertical wall edge frames 13b having a L- shaped cross section are additionally used, to more securely hold the various component members together so that they constitute a container. The modified bottom frame 6b has at each end of each vertical side a projection which fits into one of the lower holes provided in the vertical wall edge frames 13b, and the upper wall edge frames 8b are channel-shaped and they are provided at one end a projection which is inserted in the upper hole made in the vertical wall edge frames 13b and at the other end a L-shaped cut which receives the projection provided end of the adjacent upper wall edge frame 13b.

As illustrated in FIG. 17, still another embodiment of this invention comprises the same essential component members as the container construction shown in FIG. 16 except that the separate upper wall edge frames 8b are substituted by the unitary upper wall edge frame 8c which covers not only the upper edges of all the wall boards 7, 7a but also the upper edges of the vertical wall edge frames 13a thus making the use of the pack tapes l5 unnecessary in holding the wall boards together in position.

With reference to FIGS. 13A and 13B, further modified upper wall edge frames 8d are identical in shape with the previously-mentioned frames 8a and have at one end of the outside surface a hinged metallic bar 21 which is engaged with a metallic hanger 22 attached to the upper end of the outside surface of a vertical wall edge frame 13C to securely hold the loose wall boards 7, 7a together. FIG. 13B diagrammatically shows how the hinged bar 21 and hanger 22 cooperatively work. As illustrated in FIG. 14, still further modified upper wall edge frames 8e have hangers 23 at the ends of the outside surface, which hangers receive a bent bar 24, thereby serving to keep the loose or separate wall boards 7, 7a together in position. Thus the combined use of the upper edge frames and vertical edge frames as shown in FIGS. 13A and 14, will also eliminate the use of horizontally wound pack tapes in securely holding the loose wall boards together in position.

The vertical wall edge frames may be made of the same material as the upper wall edge frames, and the pack tapes or bands may be made of steel, kraft paper, or plastics such as polypropylene, polyethylene, nylon, polyester or polyvinyl chloride.

The three embodiments of container construction of this invention which have thus been described with particular reference to FIGS. 5, l6 and 17 respectively, are commonly characterized by comprising as the essential component members a pallet having a bottom frame fixed thereon and having a recess formed therein between the sloped end of the runners and the corresponding end portion of the longitudinal boards, loose wall boards demountably erected in edge to edge relation on the bottom frame-fixed pallet snugly along the inside of the bottom frame to form side and end walls of the container, a bottom board demountably placed on the bottom frame-fixed pallet and within the walls, and separate wall edge frames or a unitary upper wall edge frame. The container constructions shown in FIGS. 16 and 17 are further characterized by using the vertical wall edge frames in combination with the separate upper wall edge frames or the unitary one to more securely hold the loose wall boards together in position, although the construction shown in FIG. 16 still needs the use of pack tapes wound around the wall boards as in the case of that shown in FIG. 5.

What is claimed is:

1. In a simplified container construction including a bottom frame-fixed pallet portion and a bottomdemountable container portion mounted thereon, the bottom frame-fixed pallet portion comprising (1) a pallet composed of spaced parallel base boards, spaced parallel runners fixed on the base boards transversely thereof, longitudinal boards fixed on the runners longitudinally thereof, and spaced parallel transverse boards fixed on the longitudinal boards transversely'thereof and just above the base boards respectively, and (2) a rectangular bottom frame having a L-shaped cross section and fixed on the pallet for receiving the bottomdemountable container portion, thus allowing the bot tom frame-fixed pallet to have therein vertically free spaces through which the tines of a cargo-handling plunger may be put into, and out of, the bottomdemountable container portion.

2. The bottom frame-fixed pallet according to claim 1, wherein the runners have downwardly sloped ends and the longitudinal boards extend beyond the upper edges of the sloped ends of the runners thereby to form therebetween a recess through which ropes may be passed for loading or unloading the container.

3. A simplied container construction including a bottom frame-fixed pallet portion and a container portion mounted thereon, (A) the bottom frame-fixed pallet portion comprising (1) a pallet composed of spaced parallel base boards, spaced parallel runners fixed on the base boards transversely thereof, longitudinal boards fixed on the runners longitudinally thereof and spaced parallel transverse boards fixed on the longitudinal boards transversely thereof and just above the base boards respectively, and (2) a rectangular bottom frame having a L-shaped cross section and fixed on the pallet for receiving the container portion, thus allowing the bottom frame-fixed pallet to have therein vertically free spaces through which the tines of a cargo-handling plunger may move, and (B) the container portion comprising loose wall boards for the side and end walls of the container portion, the loose wall boards being demountably erected in edge to edge relation within said bottom frame along the vertical side thereof, and easily releasable means to hold the erected loose wall boards together in position, whereby the container can easily be assembled for shipping and disassembled as a bundle of the component members of compact size for being sent back to the user for repeated use.

4. A simplified container construction according to claim 3, wherein the runners have downwardly sloped ends and the longitudinal boards extend beyond the upper edges of the sloped ends of the runners thereby forming therebetween a recess through which ropes may be passed for loading or unloading the container.

5. A simplified container construction according to claim 3, the container portion further comprises a bottom board demountably placed within the bottom frame on the bottom frame-fixed pallet.

6. A simplified container construction according to claim 4, wherein the container portion further comprises a bottom board demountably placed within the bottom frame on the bottom frame-fixed pallet.

7. A simplified container construction according to claim 3, wherein the easily releasable holding means are pack tapes wound around the erected loose wall boards.

8. A simplified container construction according to claim 3, wherein the container portion further comprises both upper wall edge frames covering the upper edges ofthe erected wall boards and vertical wall edge frames covering the vertical edges of the wall boards, with the upper ends of the vertical wall edge frames being covered by the upper wall edge frames and the lower ends thereof covered by the bottom frame.

9. A simplified container construction according to claim 8, wherein the upper wall edge frames are in the form of a unitary rectangular wall edge frame thereby serving as a means to securely hold the loose wall boards together in position.

10. A simplified container construction according to claim 8, wherein the upper wall edge frames are locked with one another by suitable locking means so that they take a form like a unitary rectangular upper wall edge frame, thereby serving as a means to securely hold the wall boards together in position.

11. A simplified container construction according to claim 3, wherein the rectangular bottom frame has an outward projection at at least one end of each side and wherein channel-shaped upper wall edge frames having at one end a projection and at the other end a L-shaped cut in which the projection-provided end of the adjacent upper wall edge frame is inserted, and crosssectionally L-shaped vertical wall edge frames covering the vertical edges of the wall boards and having a hole at the upper end and at least one hole at the lower end are additionally used in such a manner that the projection of the upper wall edge frames is inserted in the corresponding hole provided at the upper end of the vertical wall edge frames and the projection of each side of the bottom frame is inserted in the corresponding hole provided at the lower end of the vertical wall edge frames to securely hold the loose wall boards together in position with aid of the easily releasable holding means.

12. A simplified container construction according to claim 3, wherein the erected loose wall boards are covered at each vertical edge with channel-shaped vertical wall edge frames in such a manner that the vertical edge is inserted in the recess of the frame.

UNITED STATES PATENT OFFICE CERTIFICATE DE /CORRECTION Patent NO. 3,796,939 Dated March 12, 1974 lnventofls) Hiromasa SUZUKI It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading add the following:

--FOREIGN APPLICATION PRIORITY DATA July 13, 1971 Japan U.M. 61390/71 December 6, 1971 Japan U.M. 114732/71 December 6, 1971 Japan U.M. 1147-33/71 April 27, 1972 Japan U.M 49785/72-- Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

McCOY M. GIBSON, JR. C. MARSHALL DANN Attesting Officer I l 1 Commissioner of Patents 'ORM Po-1050 (10-69) uscoMM-oc wave-P59 9 US. GOVERNMENT PRINTING OFFICE: IQS 0-365-32 

1. In a simplified container construction including a bottom frame-fixed pallet portion and a bottom-demountable container portion mounted thereon, the bottom frame-fixed pallet portion comprising (1) a pallet composed of spaced parallel base boards, spaced parallel runners fixed on the base boards transversely thereof, longitudinal boards fixed on the runners longitudinally thereof, and spaced parallel transverse boards fixed on the longitudinal boards transversely thereof and just above the base boards respectively, and (2) a rectangular bottom frame having a L-shaped cross section and fixed on the pallet for receiving the bottom-demountable container portion, thus allowing the bottom frame-fixed pallet to have therein vertically free spaces through which the tines of a cargo-handling plunger may be put into, and out of, the bottom-demountable container portion.
 2. The bottom frame-fixed pallet according to claim 1, wherein the runners have downwardly sloped ends and the longitudinal boards extend beYond the upper edges of the sloped ends of the runners thereby to form therebetween a recess through which ropes may be passed for loading or unloading the container.
 3. A simplied container construction including a bottom frame-fixed pallet portion and a container portion mounted thereon, (A) the bottom frame-fixed pallet portion comprising (1) a pallet composed of spaced parallel base boards, spaced parallel runners fixed on the base boards transversely thereof, longitudinal boards fixed on the runners longitudinally thereof and spaced parallel transverse boards fixed on the longitudinal boards transversely thereof and just above the base boards respectively, and (2) a rectangular bottom frame having a L-shaped cross section and fixed on the pallet for receiving the container portion, thus allowing the bottom frame-fixed pallet to have therein vertically free spaces through which the tines of a cargo-handling plunger may move, and (B) the container portion comprising loose wall boards for the side and end walls of the container portion, the loose wall boards being demountably erected in edge to edge relation within said bottom frame along the vertical side thereof, and easily releasable means to hold the erected loose wall boards together in position, whereby the container can easily be assembled for shipping and disassembled as a bundle of the component members of compact size for being sent back to the user for repeated use.
 4. A simplified container construction according to claim 3, wherein the runners have downwardly sloped ends and the longitudinal boards extend beyond the upper edges of the sloped ends of the runners thereby forming therebetween a recess through which ropes may be passed for loading or unloading the container.
 5. A simplified container construction according to claim 3, the container portion further comprises a bottom board demountably placed within the bottom frame on the bottom frame-fixed pallet.
 6. A simplified container construction according to claim 4, wherein the container portion further comprises a bottom board demountably placed within the bottom frame on the bottom frame-fixed pallet.
 7. A simplified container construction according to claim 3, wherein the easily releasable holding means are pack tapes wound around the erected loose wall boards.
 8. A simplified container construction according to claim 3, wherein the container portion further comprises both upper wall edge frames covering the upper edges of the erected wall boards and vertical wall edge frames covering the vertical edges of the wall boards, with the upper ends of the vertical wall edge frames being covered by the upper wall edge frames and the lower ends thereof covered by the bottom frame.
 9. A simplified container construction according to claim 8, wherein the upper wall edge frames are in the form of a unitary rectangular wall edge frame thereby serving as a means to securely hold the loose wall boards together in position.
 10. A simplified container construction according to claim 8, wherein the upper wall edge frames are locked with one another by suitable locking means so that they take a form like a unitary rectangular upper wall edge frame, thereby serving as a means to securely hold the wall boards together in position.
 11. A simplified container construction according to claim 3, wherein the rectangular bottom frame has an outward projection at at least one end of each side and wherein channel-shaped upper wall edge frames having at one end a projection and at the other end a L-shaped cut in which the projection-provided end of the adjacent upper wall edge frame is inserted, and cross-sectionally L-shaped vertical wall edge frames covering the vertical edges of the wall boards and having a hole at the upper end and at least one hole at the lower end are additionally used in such a manner that the projection of the upper wall edge frames is inserted in the corresponding hole provided at the upper end of the vertical wall edge frames and the projection of each side of the bottom frame is inserted in the corresponding hole provided at the lower end of the vertical wall edge frames to securely hold the loose wall boards together in position with aid of the easily releasable holding means.
 12. A simplified container construction according to claim 3, wherein the erected loose wall boards are covered at each vertical edge with channel-shaped vertical wall edge frames in such a manner that the vertical edge is inserted in the recess of the frame. 